1. Field
The described embodiments relate to techniques for improving communication in wireless networks.
2. Related Art
Many electronic devices, such as cellular telephones, include a networking subsystem that is used to wirelessly communicate with other electronic devices in a cellular-telephone network. For example, these electronic devices can include a networking subsystem with a cellular-telephone network interface (UMTS, LTE, etc.).
A variety of environmental and operating conditions (which are sometimes referred to as ‘circumstances’) can adversely affect communication in the cellular-telephone network. For example, many electronic devices implement thermal mitigation to manage the temperature of the electronic devices, thereby ensuring that the electronic devices meet their thermal specifications under all circumstances.
One existing thermal-mitigation technique is to restrict the radio transmit power of an electronic device. In particular, when the electronic device reaches a certain temperature, the thermal-mitigation technique may be engaged and may start the mitigation process by controlling the operation of different components of the electronic device. For example, the thermal-mitigation technique may introduce a hard cap or limit on the maximum radio transmit power until the temperature of the electronic device is reduced.
However, this existing thermal-mitigation technique can adversely impact voice and data call performance. In particular, the hard cap on the radio transmit power can result in voice and data call drop under a low-coverage mobility scenario. This is illustrated in FIG. 1, which shows received signal strength and transmit power for an existing electronic device in a cellular-telephone network. At time A, cell 1 is in the active set of the electronic device and its received signal strength is sufficient to maintain the connection. Moreover, at this time, cell 2 is not added to the active set because its received signal level is not above an add threshold, and the required transmit power of the electronic device is low and, thus, is not affected by a transmit-power cap. Then, at time B, the temperature of the electronic device reaches a maximum operating-temperature threshold and a hard cap on the transmit power is applied. Subsequently, at time C, the received signal strength of cell 2 is above the add threshold and the required transmit power of the electronic device exceeds the transmit-power cap. Even though the electronic device wants to exchange a signaling message with the cellular-telephone network to add cell 2, it may not be able to do so because of the limitation imposed by the transmit-power cap. As a consequence, by time D, the received signal strength of cell 1 may degrade to the level that it will be dropped from the active set and cell 2 is still not added to the active set because of the transmit-power cap. By time E, the electronic device is not able to sustain the call and it is dropped. Such a lost connection degrades the user experience and is frustrating to users of electronic devices.